The present invention relates to a vehicle with a hinged attachment implement. More particularly, the invention relates to a tractor operating with a plow, for example.
A vehicle such as, for example, a tractor is operated with an attachment implement such as, for example, a plow. When operating the vehicle with the attachment implement in lifted, that is, not in operating position, the vibration behavior of the implement, due to its rigid connection to the vehicle, changes in comparison to a vehicle without an attachment implement. More particularly, when operated at high speeds and/or across uneven terrain the vehicle is, due to the mass moment of inertia caused by the attachment implement, subjected to considerable pitching vibrations. This results in the static front axle load, which in any case has already been reduced by the weight of the attachment implement, being eliminated partially, or even completely. The road contact of the front wheels, which is thereby lost from time to time, prevents effective steering of the vehicle during this phase of operation, thus creating a considerable danger of accident which, in some cases, might even cause the vehicle to turn over. These pitching vibrations occur, above all, in the 0.5 to 5 Hz frequency range, and they depend essentially on the springiness of the tires, as well as on the mass and position of the center of gravity of the entire team, that is, the vehicle and the attachment implement.
Due to the forces affecting a tractor and a plow pulled by it, because of uneven terrain, acceleration of speed or brake acceleration, or similar forces, and the moments resulting therefrom, an actual pitching angle, relative to the plane of vertical deflections of the tractor, occurs during operation. The resulting deflection, relative to the static position of the tractor, results in a self-aligning torque due to the cushioning and damping characteristics of the tires or the entire wheel arrangement, which, together with the moment of inertia of the rigidly connected plow, acts upon the tractor and produces the temporary time-dependent pitching angle of the tractor. In this connection, the moment of inertia of the tractor itself must also be taken into consideration.
In order to reduce the pitching vibrations, it has been proposed to replace the rigid coupling of the attachment implement by a cushioning and damping element. The springiness and attenuation constant of the damping element are so developed that, in reference to the portion of the pitching vibration of the dynamic wheel loads, it functions as a vibration absorber. This type of coupling is fully effective only at a specific frequency. Furthermore, the dynamic wheel loads are reduced by the passive absorption of the pitching vibrations. However, the attachment implement still exercises a considerably negative influence on the pitching vibrations of the vehicle.